Study On The Chemical Components Of Ginseng And Its Anti-incidental Root-knot Nematode Activit

In this paper,crude extracts of Crotalaria juncea L in methanol（CE）,petroleum ether extract fraction（PEF）,ethyl acetate extract fraction（EAF）,n-butanol extract fraction（n-Bu F）and the remaining water fraction（WF）were prepared,and the crude extract and each fraction extract were evaluated for nematicidal activity against the second juveniles（J2）of Meloidogyne incognita（M.incognita）.The results showed that PEF had excellent nematicidal activity against M.incognita.Based on the mortality results of the J2,pot experiments on PEF aimed at investigating the EAFfect of PEF on the growth of tomato plants and their resistance to M.incognita infestation.Finally,the PEF was isolated for chemical composition and evaluated for nematicidal activity of the chemical compounds.This study provides a theoretical basis for the development of highly EAFfective,green,low toxicity nematicides of plant origin against M.incognita.（1）The J2 of M.incognita were exposed to CE,PEF,EAF,n-Bu F and WF for24 h,48 h and 72 h.The mortality of J2 was counted and the toxicidal EAFfects of CE,PEF,EAF,n-Bu F and WF on the J2 of M.incognita were evaluated.PEF showed the best nematicidal activity in the concentration range of 10-50 mg/m L,with LC₅₀ of39.91±1.84,21.80±1.71 and 14.30±1.65 mg/m L at 24 h,48 h and 78 h,respectively,while CE and WF showed almost no nematicidal activity at 24 h-72 h exposure times.The mortality of J2 was below 50%at all concentrations at 72 h.The LC₅₀ for EAF was 28.56±1.46 mg/m L at 72 h.（2）Based on the nematicidal activity of the CE,PEF,EAF,n-Bu F and WF against the J2 of M.incognita,PEF was obtained to have the best nematicidal activity against the J2 with the highest number and content of compounds.The EAFfect of PEF on the growth and EAFence of tomato plants against M.incognita infestation was evaluated in pot experiments,and PEF significantly improved the growth and agronomic traits of nematode-infested tomato plants.There was no dwarfing of tomato plants,no leaf degradation and no yellowing of leaves,and tomato plant height,above-ground fresh weight,root length and root fresh weight were increased.PEF also inhibited the infestation of tomato plants by the M.incognita,reduced the formation of root nodules in the roots of tomato plants,decreased the root-knot index and promoted the growth and development of tomato plants.（3）Related d EAFence enzymes play an important role in the plant-induced resistance response.Superoxide dismutase（SOD）,catalase（CAT）,peroxidase（POD）,polyphenol oxidase（PPO）,lipoxygenase（LOX）and phenylalanine lyase（PAL）are some of the enzymes that play a role in plant resistance.Results from pot experiments showed that infestation of tomato plants by M.incognita reduced the enzyme activities of SOD,CAT,POD,PPO,LOX and PAL in the roots of tomato plants,leading to the accumulation of lipid peroxides along with a reduction in the activity of the relevant antioxidant enzymes,as well as a reduction in the content of total phenols,total flavonoids,lignin and jasmonic acid.The activity of SOD,CAT,POD,PPO,LOX and PAL enzymes in tomato plants could be up-regulated compared with that in nematode infection when PEF was applied to the soil,involved in the relevant metabolic pathways,promoted the synthesis of total phenols,total flavonoids,lignin and jasmonic acid,reduced the malondialdehyde（MDA）content,improved the resistance of the tomato plant to the M.incognita,improved the agronomic traits of the tomato plant and promoted the growth of the tomato plant in a more obvious way.（4）A total of 13 compounds were isolated and identified from the PEF.13compounds were identified as 28-O-Laurylbetulin（1）,betulinic acid（2）,（Z）-9-eicosenoi acid（3）,bakuchiol（4）,angelicin（5）,crotafuran A（6）,erystagallin C（7）,phthalic acid bis-（2,5-dimethyl-hexyl）（8）,α-dimorphecolic acid（9）,12-hydroxybakuchiol（10）,bavachinin（11）,psorachalcone A（12）and isobavachalcone（13）.（5）13 compounds were screened for nematicidal activity.Second instar southern root-knot larvae were exposed to 6.25-100μg/m L of sample solution,and compound11 and compound 13 showed excellent nematicidal activity.The LC₅₀ for compound13 was 55.64μg/m L at 24 h,43.90μg/m L at 48 h and 26.61μg/m L at 72 h.The remaining compounds were less EAFfective in killing nematodes.PEF showed excellent toxic EAFfect on the J2 of M.incognita.Meanwhile,PEF also systematically increases resistance to nematode infestation and promotes the growth of tomato plants when applied to the soil in which they are grown.Some of the monomeric compounds isolated and identified from PEF have nematicidal potential.In summary,Crotalaria juncea L.can be used as a natural plant source for the control of M.incognita.